[Kevin Sevcik]

Related questions that spring to mind are if you checked that the output shaft turned freely before powering the motors, if you were running the motors through an appropriate breaker, if you put the e-clip on the output shaft, etc, etc.

Given the super slippery floor this year, I can't see a freely rotating drivetrain doing this to a toughbox. Nor should you be able to do easily do this with appropriate breaker protection on the drive train.

The only way I can think of for a nice loose drivetrain to do this to a gear is if you have some wicked shock loading on it from your control system going from full forward to full reverse instantly and repeatedly.